Before proceeding with troubleshooting, take note of the following precautions:
TIMING LIGHT USE
Care should be exercised when connecting a timing light or other pick-up equipment. Do not force anything between the boots and wiring, or through the silicone jacket. Connections should be made in parallel using an adapter. Inductive pickup timing lights are the best kind to use with the ignition systems covered by this guide.
SPARK PLUG WIRES
The plug wires used with these systems are of a different construction than conventional wires. When replacing them, make sure you get the correct wires, since conventional wires will not carry the voltage. Also, handle the wires carefully to avoid cracking or splitting them, and NEVER pierce the wires.
Not all tachometers will operate or indicate correctly when used on an HEI or C 3 I system. While some tachometers may give a reading, this does not necessarily mean the reading is correct. In addition, some tachometers hook up differently from others. If you cannot figure out whether or not your tachometer will work on your car, check with the tachometer manufacturer.
The tachometer terminal should never be allowed to touch ground, as damage to the computer control module and/or ignition coil assembly can result.
When disengaging connectors, do not use a screwdriver or other tool to release the locking tab, as this might break the connector.
Instruments designed specifically for testing HEI or C 3 I systems are available from several tool manufacturers. Some of these will even test the module itself. However, the tests given in the following information will require only an ohmmeter and a voltmeter.